Photographic developer.



PHOTOGBAPHIC DEVELOPER.

1,158,0Hl1l.

No Drawing.

.To all whom it may concern:

Be it known that I, CHARLES J. THATGHER, a citizen of the United States, and a resident of New York city, in the county of New York and State of New York, have invented certain new and useful Improvements in Photographic Developers, of which the following is a specification.

This invention relates to improvements in the use of photographic developers.

The object of the invention is to so regulate the action of a photographic developer as to provide a satisfactory substitute for rapid and expensive developers like metol mono-methyl-paramidophenol sulfate) and it has for its further object to effect such regulation of photographic development with out producing undesirable or inferior results.

At the present time the organic compound, monomethyl paramidophenol sulfate, usually called metol, is perhaps the most rapid and at the same time most expensive photographic developer in general use. In commercial photography, at least, it has hitherto not been possible to substitute other cheaper developers for the specified compound, principally because of the lesser speed of development of such other developers. Where large numbers of negatives or positives have to be developed each day, as in the production of moving picture films, it is important that the development should be as rapid as possible. The extreme rapidity of the reducing action of monomethyl paramidophenol sulfate upon silver salts, accounts, in a large degree, for its exclusive use-despite its high costin combination with hydroquinone, in commercial photography. I have found that other cheaper developers, paramidophenol sulfate, for example, may be satisfactorily used, either alone or mixed with hydroquinonefor example, and produce as rapid or more rapid development of the latent image, provided the proper conditions, which I herein disclose, are employed. In the development of moving picture films, for example, paramidophenol sulfate may, by my invention, nowbe substituted for the monomethyl derivative thereof, and produce the same speed, color, density, contrast, etc. with the same formula, by the improvement which I will hereinafter describe.

In the development of moving picture Specification of Letters Patent.

Patented Hot. 208, 1915.

Application filed March 22, 1915. Serial No. 16,286.

velopment of a normally printed positive,

from two to five minutes. If paramidophenol sulfate is substituted for the monomethyl derivative thereof, using the other ingredicuts, the development of the same positive requires twice as long. Attempts which have been made to substitute paramidophenol sulfate or hydrochlorid in place of metol have failed and have been abandoned because of the longer time required for the development of the plates or films. I have succeeded in overcoming this difficulty attending the use of paramidophenol and similar developing compounds, by adding a relatively small amount of sodium or potassium hydrate to the developing solution as ordinarily prepared and used. i

In the development of moving picture films, for example, I may use the following formula for mixing up the developing solution, as a representative formula.

Water 800 parts. Paramidophenol sulfate .5 Hydroquinone 2 Sodium sulfite 20 Sodium carbonate l i Potassium bromid .5 Sodium hydrate 1 The use of 1 part of sodium hydrate in a developing solution containing these constituents and proportions, is, I find, sufficient to regulate the development so that substan-' tially the same results are obtained and in substantially the same time as with a metolhydroquinone developer of the same composition, but Without the sodium hydrate. I give these proportions only by way of example. The proportions'may be varied and in some instances it may be necessary to use a larger proportion of sodium hydrate, for example, 2 parts thereof. An equal weight of paramidophenol sulfate may be similarly substituted for the metol in any developing solution formula by adding a sufficient quantity of sodium hydrate to give substantially the sa'merapidity of development asdoes the metol developing solution. Generally the proportion of sodium hydrate necessary will be between 1/ and 1/30 of the amount ophenol, have been made and used hereto fore with sodium hydrate or other caustic alkalis in place of sodium carbonate. An example of such a developer now in use is rodinal. But for commercial photography, where a largequantity of developing solution is made up at one time and used continuously for a number of days until exhausted, it has been found impossible to economically and satisfactorily use a developing solutionof this nature, containing, in addition to the other usual ingredients, a

v 'caustic alkaline solution of paramidophenol or of the same and hydroquinone. In the first place sufficient amount of sodium hydrate caused a rapid and unpermissible deterioration of the developing solution by oxidation. Moreover, a solution containing such a quantity of sodium hydrate (Without sodium carbonate) caused frilling of the'gelatin or partly dissolved it, or produced a mottled efiect which became noticeable when the image was projected upon a screen. But by mixing up the developing solution with both the hydrate and the carbonate of sodium or' of potassium, and in suitable proportions as previously specified, instead of either the hydrate or carbonate alone, I am able to avoid the disadvantageous effects attending the use of the hydrate alone, and amable to increase, to the necessary degree, the speed of development over that which is obtainable with carbonate alone.

I believe that the explanation of the effect herein disclosed, viz: that a stable, rapid developing solution may be produced by the use of a relatively small proportion of sodium hydrate with the carbonate, is found in the following reaction, which occurs when alkaline carbonates are dissolved in water. Neglecting the sodium anions and considering only the cathions, this reaction is:

C0,, 11 0:1100; OH This is a reversible reaction and an equilibrium, is constantly maintained between the concentration of the various components of the system. When the hydroxyl-(OH concentration is increased, as I do by adding a small amount of sodium hydrate, the reaction proceeds from right to left, partially reducing the concentration of the OH and of the HCO ions, and correspondingly increasing the concentration of the CO ion and of water until the equilibrium is restored. The concentration of hydroXl ions in the solution, at any time, therefore, is not as great as that due to the sodium hydrate alone nor to the sum of this concentration and that due to the sodium carbonate, so that oxidation and deterioration, which varies directly as the hydroxyl concentration, is much slower than in a sodium hydrate solution alone. On the other hand, as the hydroxyl ion concentration tends to decrease during the use of the developing solution, it is restored by the reaction proceeding from left to right to maintain the equilibrium.

It will be understood that my invention may be used for the production of stable, rapidly developing solutions of other developing compounds than paramidophenol sulfate, or of mixtures thereof with hydroquinone, and that suitable changes in the ingredients and proportions hitherto specified may be made by those skilled in the art without departing from the scope of my invention.

I claim:

1. The process of rapidly developing the latent image of an exposed, sensitized photographic surface which consists in subjecting the exposed sensitized surface to the action of a solution containing hydroquinone and a relatively smaller proportion of paramidophenol sulfate; an alkali sulfite; an alkali carbonate, and a relatively small proportion of sodium hydrate.

2. The process of rapidly developing the latent image of an exposed sensitized photographic surface, which consists in subjecting the exposed sensitized surface to the action of a solution containing paramidophenol sulfate, an alkali sulfite, alkali carbonate,

and an alkali hydrate in the proportion of 1/10 to 1/30 of the alkali carbonate.

3. A rapid, substantially stable photographic developing solution, consisting of a solution in water of hydroquinone, paramidophenol sulfate, alkali sulfite, an alkali carbonate, and sodium hydrate in relatively small proportion to the alkali carbonate. 4. A rapid developing agent for sensitized photographic surfaces, containing paramidophenol sulfate, a preservative, an alkali carbonate, and sodium hydrate in relatively small proportion to the alkali carbonate.

5. A rapid developing agent for sensitized photographic surfaces, containing paramidophenol sulfate, an alkali carbonate, andan alkali hydrate in the proportion of .1/10 to 1/30 of the alkali carbonate.

6. A rapid, substantially stable, photographic developing solution, consisting of a solution in Water of hydroquinone, 2 parts; paramidophenol sulfate, 1/2 part; sodium sulfite, parts; sodium carbonate, 14 parts; potassium bromid, 1/2 part; sodium hydrate, 1 part; all by Weight, substantially as described.

7. A rapid, substantially stable, photographic developing solution, consisting of a solution in Water of hydroquinone, a paramidophenol salt, a preservative, an alkali carbonate, and sodium hydrate in relatively small proportion to the alkali carbonate.

8. A rapid developing agent for sensitized photographic surfaces, containing paramidophenol sulfate, alkali carbonate, and an alkali hydrate in the proportion of 1/10 to 1/30 of the alkali carbonate.

9. A rapid, substantially stable, photographic developer, containing hydroquinone, paramidophenol sulfate, a preservative, an alkali carbonate, and sodium hydrate in relatively small proportion to the alkali carbonate.

10. A rapid, substantially stable, photographic developer, containing hydroquinone, paramidophenol sulfate, a preservative, an alkali carbonate, and sodium hydrate in the proportion of 1/10 to l/30 of the alkali carbonate.

11. A rapid, substantially stable, photographic developing solution, consisting of a solution in Water of hydroquinone, paramidophenol sulfate, a preservative, a restrainer, an alkali carbonate, and sodium hydrate in relatively small proportion to the alkali carbonate.

Signed at New York city in the county of New York and State of New York this 20th day of March A. D. 1915.

CHARLES J. THATCHER.

Witnesses:

ARTHUR WoRsoHEK, LAURA E. SMITH. 

